Approximately five percent of the United States' primary energy is consumed providing illumination in commercial and industrial buildings. Roughly another three percent is consumed for cooling these buildings. As energy costs climb higher, methods of reducing lighting and cooling costs are becoming more important. The present invention provides a method for reducing building lighting and cooling costs by projecting daylight deep into the interior of a building space. This provides two distinct advantages. First, ordinary sources of artificial lighting which consume electrical energy can be reduced or eliminated. Second, the reduction of artificial light sources provides the ancillary benefit of reducing the heat which usually accompanies the lighting source, thus reducing cooling costs as well. In addition, since the color rendering and luminous efficacy of sunlight is generally superior to that of artificial light, sunlight provides more aesthetically pleasing light than artificial light.
Traditionally, clerestories, horizontal baffles (light shelves), glass blocks with built-in refracting prisms, and various configurations of louvers (venetian blinds) have been employed to project daylighting admitted through wall apertures into interior spaces. Also, light wells or atria have been traditionally used to admit daylight into multistory structures. Although beneficial, these methods are fraught with limitations.
Specifically, not all methods of projecting daylight into buildings actually result in energy savings due to inefficient designs. Other methods require that a building and its mechanical systems be specifically designed to accommodate the daylighting device. Still others are limited because they operate optimally only at one time during the day or one day during the year, since they do not account for the movement of the sun across the sky throughout the day or for different heights of the sun at different times during the year. Other daylighting devices are expensive to construct or unattractive when positioned on a building.